Plate type heat exchangers

ABSTRACT

A heat exchanger is described which is adapted for use with a regenerative type gas turbine engine. The heat exchanger comprises a stack of annular disc plates which are joined in bellows fashion. Inlet and exit plenums extend longitudinally of the stack. The plates define alternate flow paths respectively for radial flow of the hot gas discharge outwardly from the center of the stack and for cross flow of pressurized air from the inlet to exit plenums. Alternate plates are provided with flow path defining corrugations formed both radially, in a general sense, and cross wise, generally concentric of the discs. The remaining plates have generally radially extending, flow paths defining corrugations. The radial corrugations of all plates are curved to be generally concentric of the curved sides of the inlet and exit plenums which are respectively triangular and elliptical in cross section.

United States Patent [191 Stein et a1.

[451 Aug. 27, 1974 1 PLATE TYPE MAT EXCHANGERS [75] Inventors: Wolfgang.1. Stein, Milford;

Salvatore Straniti, Orange, both of Conn.

[73] Assignee: Avco Corporation, Stratford, Conn. [22] Filed: Nov. 16,1972 [21] Appl. No.: 307,264

[52] 11.5. C1. 165/166 [51] Int. Cl. F28b 3/12, F28b 13/06 [58] Field ofSearch 165/164-167 [56] References Cited UNITED STATES PATENTS 2,368,7322/1945 Wallgren 165/167 2,469,028 5/1949 Belaieff 165/166 2,877,0003/1959 Person 165/166 X 3,228,464 1/1966 Stein et al 165/166 3,424,240l/l969 Stein et a1, 165/166 Primary Examiner-Charles J. Myhre AssistantExaminer-Theophil W. Streule, .lr. Attorney, Agent, or Firm-Charles M.Hogan; Irwin P. Garfinkle [57] ABSTRACT A heat exchanger is describedwhich is adapted for use with a regenerative type gas turbine engine.The heat exchanger comprises a stack of annular disc plates which arejoined in bellows fashion. Inlet and exit plenums extend longitudinallyof the stack. The plates define alternate flow paths respectively forradial flow of the hot gas discharge outwardly from the center of thestack and for cross flow of pressurized air from the inlet to exitplenums. Alternate plates are provided with flow path definingcorrugations formed both radially, in a general sense, and cross wise,generally concentric of the discs. The remaining plates have generallyradially extending, flow paths defining corrugations. The radialcorrugations of all plates are curved to be generally concentric of thecurved sides of the inlet and exit plenums which are respectivelytriangular and elliptical in cross section.

7 Claims, 11 Drawing Figures AIR FROM COMPRESSOR 20 A Is H ll lll Illlllllllll AS |oj n j HOT GAS 26 E DISCHARGE \Y I s, 2 AIRTOllllllllll1lII\1I|||1lH COMBUSTOR H Q I I II I II II l 11 I I1 I I IHAusTk PAIENTEBMIE asa em AIR FROM COMPRESSOR HOT GAS DISCHARGE AIR TOCOMBUSTOR PAIENTEDAUBZYIW 3', 8 a 1,674

' mm w 4 HOT GAS ENE [S DIS HARG FEE T W COMPRESSOR AIR HOT GAS v QPMDISCHARGE E The present invention relates broadly to heat exchangersand more particularly to improvements in plate type heat exchangers.

Many different types of heat exchangers are known for transferring heatto or from a fluid, usually transferring heat between two fluid mediums.

in almost all heat exchangers, the rate of heat transfer is of primeconcern. This factor is of particular importance where heat exchangersare used in regenerative type gas turbine engines. Briefly, in suchengines, waste energy of the hot gas stream exhaust is transferred,through a heat exchanger, to a pressurized air stream as it passes fromthe engines compressor to its combustor. Thus the energy level of thehot gas stream generated in the combustor is proportionately increasedto give an overall, theoretical, increase in en'- gine cycle efficiency.

Heat exchangers for regenerative type engines not only require a highrate of heat transfer, but also require a minimum impedence or pressureloss to the flow of the pressurized air and the hot gas streamstherethrough. Otherwise, excessive pressure drops in either or both ofthe fluid flow paths could cause losses which more than offset thetheoretical gains to be de rived from the regenerative cycle. Anotherfactor of concern in such heat exchangers, is the wide range oftemperatures encountered in cyclic operation and the resultant stressesthat are induced in the component parts of the heat exchanger. Yet,another area of concern in heat exchangers for regenerative typeengines, particularly engines utilized for 'the propulsion of aircraft,is the need for a lightweight construction as well as a configurationhaving a minimum space envelope.

Plate type heat exchangers, while having other applications, have beenfound particularly effective in fulfilling the needs described above forregenerative type gas turbine engines. A particularly effective heatexchanger of this type is disclosed in US. Pat. No. 3,424,240. In thatheat exchanger, a stack of corrugated plates, in the form of annulardiscs, define a central entrance for the hot gas discharge of theturbine engine. From this central entrance, thehot gasses pass radiallyoutwardly between alternate pairs of plates to a discharge duct.Pressurized air from the engine compressor flows into inlet plenumsextending longitudinally of the stack of plates, through cross flowpaths between the plates, to exit plenums, also extending longitudinallyof the stack of plates and then back to the combustor of the engine.

One object of the invention is to increase the overall effectiveness ofstacked plate type heat exchangers of the general configurationreferenced above, and in so doing, to particularly combine a high rateof heat transfer with a low impedence to fluid flow in a compact,rugged, lightweight construction.

Another and broader object of the invention is to improve theeffectiveness of plate type heat exchangers and particularly to increasethe rate of heat transfer capabilities thereof as well as reducing thepressure drops of fluid flows therethrough and further to decrease theinduced stresses imposed thereon during operation.

The above ends, in accordance with the broader as pects of theinvention, are attained in a heat exchanger which includes a relativelythin plate defining on its op- 2 posite sides, opposed portions of flowpaths for first and second fluids. This plate is characterized by havingfirst and second series of corrugations with one series being crosscorrugations generally at right angles to the other.

The heat exchanger, preferably, further includes a pair of platesdisposed on opposite sides of the first plate and respectively definingthe opposite bounds of the two fluid flow paths. The second plates alsohave a series of corrugations which are of the same spacing as andaligned with one of the series of corrugations of the first plate.Further, the corrugations of the second plates are out of phase withcorrugations of the first plate to define flow paths having longitudinaland cross sections which vary in area. Further, it is advantageous thatone of the series of corrugations of the first plate have a lesserheight than the other series of cross corrugations thereof and that thecorrugations of the second plates are generally aligned with the lowerseries of corrugations of the first plate.

In a more specific aspect of the invention, a plurality of first andsecond plates are formed as annular discs and are arranged in stackedrelationship to define alternate flow paths for the first and secondliquids. Further, longitudinal inlet and exit plenums may be providedthrough the plates for the introduction and discharge of the firstliquid. As specifically adapted for use with a regenerative type gasturbine engine, the inlet plenum would receive pressurized compressorair and the exit plenum .would discharge air to the combustor of theengine after the air passes through cross flow, heat exchange flow pathsbetween alternate pairs of plates. The second fluid would be the hot gasdischarge of the engine which passes through flow paths radial of thestacked discs.

The second plates, in disc form, have series of corrugations betweenadjacent plenums which extend, generally, in a radial direction. Thefirst series of corrugations of the first plates also extend radiallybetween adjacent plenums, while the higher, cross corrugations areformed generally concentric of the discs and engage the second platecorrugations on opposite sides.

Further, the first and second plates may have flanges peripherally oftheir inner and outer diameters. The flanges of the first plates projectin one axial direction and the flanges of the second plates project inthe opposite direction in matching relationship with flanges of theadjacent plates. These matching flanges are respectively joined tocomplete the cross flow paths for the pressurized air. Further, thelongitudinal plenums may be defined by openings in the first and secondplates. The surfaces of the adjacent first and second plates, oppositeof the joined plenums thereof, may be joined peripherally of suchopenings so that the stack of plates becomes a bellows.

Another preferred feature is found in providing radial corrugationsadjacent the plenum openings which direct air flow laterally to anentrance chamber for radial flow through a primary heat transfer zoneand then to a discharge chamber leading to the exit plenum. Crosscorrugations of a lesser height as well as the reduced height radialcorrugations are formed in the first plates in the areas of thesechambers to facilitate cross flow with a maximum heat transfer.

Another feature of the invention is found in forming each inlet plenumwith a generally triangular cross section and each exit plenum witha'generally elliptical cross section having its major axis extending ina radial direction. The generally radial corrugations of the first andsecond plates are then formed generally concentrically of the adjacentsides of the plenums. This feature of the invention may also be utilizedin combination with first plates having other forms of corrugations.

The above and other related objects and features of the invention willbe apparent from a reading of the following description of a preferredembodiment thereof, in which reference is made to thhe accompanyingdrawings, and the novelty thereof pointed out in the appended claims.

In the drawings:

FIG. 1 is a longitudinal cross section of a heat exchanger in which thepresent invention is embodied;

FIG. 2 is an enlarged view of a fragmentary portion of FIG. 1;

FIG. 3 is a perspective view, partially exploded, of a stack of platescomprising the present heat exchanger;

FIG. 4 is a fragmentary perspective view, on a greatly enlarged scale,looking generally in the direction of arrow A in FIG. 3 and illustratinga pair of plates which define an airflow path through the heatexchangers;

FIG. 5 is a fragmentary perspective view, on a greatly enlarged scale,looking generally in the direction of arrow B in FIG. 3 and illustratinga pair of plates defining a portion of the hot gas flow path of the heatexchanger;

FIG. 6 is a section taken on line 66 in FIG. 4, on an enlarged scale;

FIG. 7 is a section taken on line 7-7 in FIG. 4, on an enlarged scale;

FIG. 8 is a section taken on line 88 in FIG. 4, on an enlarged scale;

FIG. 9 is a section taken on line 9-9 in FIG. 4, on an enlarged scale;

FIG. 10 is a section taken on line 10-10 in FIG. 4, on an enlargedscale; and

FIG. 11 is a section taken on line 11-ll in FIG. 4, on an enlargedscale.

The heat exchanger, illustrated in FIG. 1 and indicated by referencecharacter 10, is adapted for attachment to a gas turbine engine at apoint downstream of the final turbine stage of that engine. The engine,itself, may be of conventional construction in accordance with wellknown designs for regenerative type engines. The hot gas discharge ofthe engine enters the center of the heat exchanger 10 and then isdirected radially outwardly, through a stack of plates 11, to an exhaustsystem which includes a surrounding duct 12. The heat exchanger 10comprises an adaptor frame 14, which may be attached to a frame memberof the engine. The adaptor frame 14 has a plurality of passageways 16and 18 which respectively connect with engine passageways (not shown)leading from the engines compressor and leading to the enginescombustor. The compressor passageways 16 are aligned with a plurality ofinlet plenums 20, see also FIG. 3, formed longitudinally through thestack of plates 11. The combustor passageways 18 are aligned with aplurality of exit plenums 22 also extending longitudinally through thestack of plates 11. Cross flow paths between adjacent plenums 20 and 22provide the primary heat exchange between the radially flowing hot gasdischarge and the pressurized compressor air. These cross flow andradial flow paths will presently be described in detail. The heatexchanger 10 further comprises an end frame 24 and an end plate 26,which define the downstream limit of the hot gas discharge flow path sothat all of the hot gasses may be turned radially outwardly through thestack of plates 11 and discharged through the exhaust system.

The stack of plates 11, FIG. 3, comprises a series of alternatelyarranged plates 11a and 11b, which are identical in outline and differprimarily in the flow path defining corrugations formed therein. Theplates 11a and 11b are in the form of annular discs having inner andouter flanges 28 and 29. The flanges of the plates 11a project in oneaxial direction and the flanges of the plates 1111 project in theopposite axial direction (FIGS. 2 and 4). Successive pairs of plates 11aand 11b are thus disposed with their flanges 28 and29 in face-tofacerelation. These matching flanges are seam welded or otherwise joinedaround their full circumferences. The pairs of plates, thus joined,define the bounds of the cross flow paths between plenums 20 and 22.

The plenums 20 and 22 comprise aligned openings 20a, 20b and 22a, 22b,formed in the plates 11a and 11b respectively. The surfaces of plates11a and 11b facing outwardly of the flange welds are joined, as bywelding, peripherally of the openings 22a, 22b, and 20a, 20b, FIGS. 2and 5. The stack of plates 11 is thus joined in fashion. fashion Thepairs of plates 11a and 11b define alternate flow paths for thepressurized air and the hot gas discharge as well as the plenums 20 and22. The stack of plates 11 may further be formed as a series ofsubstacks as taught in US. Pat. No. 3,385,353. With such an arrangement,and as indicated in FIGS. 1 and 2, a selected number of plates 11a and11b are joined as just described and their opposite ends are secured tosomewhat thicker intermediate plates 30 which have openingscorresponding to the openings 20a, 20b, and 22a, 22b, and which furtherhave positioning lugs, that are located by rods 32 extending the fulllength of the stack 1 1.

Referencing next FIG. 4, it will be noted that the openings 22a and 22bare generally elliptical and that the openings 20a and 20b are generallytriangular and that the adjacent sides of each opening 20 and 22 aresimilarly curved, or generally concentric. This relationship, maximizesthe heat transfer area of the discs and minimizes the overall volume, orspace envelope, of the heat exchanger, when coupled with correspondlycurved corrugations in the plates 11a and 11b as shown in FIGS. 4 and 5.

More specifically, each of the plates 11a has a series of corrugations34 between adjacent openings 20a and 22a. The corrugations (see alsoFIGS. 6-11) are generally sinusoidial or what will herein be referencedas regular wave-form. The wave form corrugations 34 extend, generallyradially, from theinner flange 28 to the outer flange 29 and are furthercurved, to correspond to the curvature of the sides of the openings 20aand 22b between which they extend. Each plate 11b is corrugated in amore involved fashion. First, there are flow path defining corrugations36 and 38 which extend marginally of the openings 22b and 20brespectively. The corrugations 36 and 38 are curved similarly to thewave-form corrugations 34 and are "out of phase therewith so as tosealingly engage matching corrugations 34 respectively adjacent theopenings 22a and 20a. The corrugations 36, on opposite sides of the exitplenum opening 22, extend inwardly from the outer flange 29b andterminate at a pointspace outwardly of the inner flange 28]). In asimilar fashion, the corrugations 38, on opposite sides of each inletplenum 20a, extend outwardly from the inner flange 28b and terminate inspaced relationship from the outer flange 29b. Between the corrugations36 and 38, is a series of corrugations 40 of an intermediate height,which have a similar curvature to the curvature of the corrugations 34,are of the same spacing and also out of phase therewith. It will also beseen that the series of corrugations 40 extend from the inner flange 28bto the outer flange29b. Further, there is a series of cross corrugations42 extending between the co-extensive portions of the corrugations 36and 38. The corrugations 42, generally at right angles to thecorrugations 40, are generally concentric of the axis of the discs 11and have a spacing generally matching that of the corrugations 40. Theheighth of the cross corrugations 42 matches that of the corrugations 36and 38, so that there is a grid of engagement points between thecorrugations 34 and 42 within the boundary defined by the co-extensiveportions of the corrugations 36 and 38, herein referenced as a zone ofprimary heat transfer. In the areas above and below, are inlet and exitchambers, which have a waffle type surface formed by the intermediatecorrugations 40 and cross corrugations 44 which are of thesameintermediate height.

The described configuration of the plates Ila and llb defines cross flowpaths from one inlet plenum 1.20 to the adjacent exit plenums 22 oneither side thereof. The outer grid work of the intermediate heightcorrugations 40 and 44 form a lateral entranch chamber defined at theleft hand end thereof by the linear engagement between the corrugation36 and its matching .corrugation 34.From this lateral entrance chamber,the cross flow path extends radially inwardly between the co-extensiveportions of the corrugations 36 and 38, forming a zone of primary heattransfer, and then through a discharge chamber similar to the entrychamber described above except that the opening thereof directs the airtowards the plenum 22.

It will be noted that the'cross flow path described, provides throughoutits length, a varying cross sectional area and longitudinal sectionalarea which minimizes the boundary layers and thus increases the rate ofheat transfer. Further, it will be noted that in the grid ofcorrugations in the primary heat transfer zone, between the co-extensiveareas of corrugations 36 and 38, the variations in the flow path areabecome more pronounced for greater heat transfer effectiveness. This isopposed to the entry and exit chambers which, while providing flow areavariation, also facilitate lateral flow of the air to facilitate itsentry and discharge from the primary area.

Using FIG. 4 as a point of reference. the corrugations to the right ofthe opening 20b between the next adjacent opening 22 would define thesame series of an entry chamber, primary exchange zone and dischargechamber as described above. In both instances, the air, from the inletplenum 20, enters the outer corner of the grid work and flows radiallyinwardly. This is to say that air passing through the plenum 20 has asplit cross flow :path to both of the adjacent plenums 22 and similarlyboth of the plenums 22 receives cross flow from the plenums 20 on eitherside thereof, as is also indicated in FIG. 3.

Referencing next FIG. 5. Plates Ila and 1 1b are illustrated as theydefine a portion of the radial flow path for the hot gas dischargethrough the stack of plates. As will be seen, the corrugations 34 alsoform a grid of contact points with the cross corrugations 42, in theplate llb, to form a flow path for the hot gas discharge (see also FIGS.61 I) which varies greatly in area from the inner circumference from theplates 11a and llb to the outer circumference thereof.

It will also be noted that in each instance, the secondary flow of thepressurized air from the passageways 20 to the passageways 22 is counterto the flow of the hot gas stream in the primary area of heat exchange.

All of these factors contribute to a high rate of heat exchange forgreater efficiency. Further, the described configuration of both thecross flow paths of the pressurized air and the flow paths of the hotgas discharge have proven to be highly effective in minimizing pressuredrops so as to minimize the decrement to overall cycle efficiency whichis attributable to such losses.

Yet another factor to be noted is that the described corrugations of theplates 11a and 11b contribute to the overall efficiency of the heatexchanger in that the spring effect, or resilience, of these corrugatedplates minimizes induced stresses in the plates which are inherent inany operation in a high temperature environment as described. This is tosay that in a cyclic operation of the engine heat exchanger, the platesllu and llb will contract and expand exerting compressive forces on theplates themselves which vary in magnitude during operational cycles. Theresultant low stresses achieved enable, for a given plate material, useof thinner section material which further contributes to the efficiencyof heat transfer. The ability to utilize thinner section material forthe plates llu and llb also minimizes the overall weight heat exchanger,to the end that its incorporation in a gas turbine engine used for thepropulsion of aircraft becomes more efficient in that the overallaircraft system.

While a preferred embodiment has been described, particularly directedtowards an application in a gas turbine engine, variations of thisembodiment will occur to those skilled in the art for such anapplication and other variations thereof will be apparent forutilization in other applications of heat exchangers. The broaderaspects of the invention, as well as the full spirit and scope thereof,are therefor to be derived solely from the following claims.

Having thus described the invention, what is claimed is novel anddesired to be secured by Letters Patent of the United States is:

l. A heat exchanger comprising inlet and outlet connections respectivelyprovided for first and second fluids,

a relatively thin, first plate having first and second series ofcorrugations, one series being disposed, gen erally, at right angles tothe other,

a pair of second plates disposed, respectively, on opposite sides ofsaid first plate, said second plates, in combination with said firstplate, defining, on opposite sides thereof, portions of flow pathsbetween the respective inlet and outlet connections for the first andsecond fluids,

said second plates each having a series of corrugations generallyaligned with the first series of corrugations of the first plate andgenerally at right angles to the second series of corrugations, or crosscorrugations, of the first plate,

whereby opposite sides of the first plate define portions of the heatexchange flow paths for both the first and second fluids, which flowpaths provide a maximum of turbulence by area variations bothlongitudinally and transversely of the flow direc tions, with a minimumimpedence to fluid flow.

2. A heat exchanger as in claim 1 wherein the cross corrugations of thefirst plate engage the corrugations of the second plates on oppositesides thereof, and the corrugations of said first series are of a lesserheight than that of the cross corrugations, the spacing of thecorrugations of said first series matches the spacing of thecorrugations of the second plates, the corrugations of said first seriesare out of phase with the corrugations of the second plates. 3'. A heatexchanger as in claim 2 particularly adapted for use in combination witha gas turbine engine to increase the energy level of pressurized air(first fluid) by transferring heat thereto from the hot gas (secondfluid) discharge of the engine as the pressurized air passes from theengines compressor to its combustor, said heat exchanger furtherincluding successive first and second plates, the latter also beingrelatively thin, alternately disposed and defining alternate heatexchange flow paths for the pressurized air and the hot gas, said firstand second plates being in the form of annular discs forming a centralentrance connection for the hot gas and an outer outlet connectiontherefor, said discs also including longitudinal plennums, formed byopenings therethrough, providing the inlet and outlet connections forthe pressurized air to and from the heat transfer flow paths defined bythe first and second plates, and further wherein the corrugations of thesecond plates extend generallyradially of the discs and open to theinner and outer portions thereof to connect the heat exchange flow pathsfor the hot gas to the inlet and outlet connections therefor.

4. A heat exchanger as in claim 2 wherein adjacent first and secondplates have inner and outer peripheral flanges respectively joined toform the heat exchange flow path for the pressurized air therebetween asthe pressurized air flows from the inlet to the outlet plennums, and

pairs of plates so joined are in turn joined to adjacent pairs byseaming peripherally of the plennum openings therein, whereby the discsare connected in bellows fashion with the several heat exchange flowpaths for the pressurized air and the hot gas, respectively, separatedfrom each other.

5. A heat exchanger as in claim 4 wherein each plate has radial, flowpath defining corrugations of the same height as the cross corrugations,said flow path defining corrugations being being disposed on oppositesides of the inlet plennum openings and extending from from the innerperipheral flanges and terminating in radially spaced relation from theouter peripheral flanges, said flow path defining corrgations also beingdisposed on opposite sides of the outlet plennum openings and ex tendingfrom the outer peripheral flanges and terminating in radially spacedrelation from the inner peripheral flanges,

said flow path defining corrugations engaging corrugations of the secondplate with which it is paired, to define the lateral bounds of thepressurized air flow paths between adjacent plennums, said crosscorrugations being spaced from the inner and outer flanges, whereby thepressurized air is directed from outer, inlet chambers, radiallyinwardly through primary zones of heat transfer and then through inner,exit chambers, and further wherein the first series of corrugations ofthe first plates extend radially to the inner and outer flanges thereofand cross corrugations of the same intermediate height are formedinwardly and outwardly of the full height corrugations to provide awaffle effect in the portions of the first plates which define the inletand exit chambers.

6. A heat exchanger as in claim 5 wherein there are a plurality of inletand outlet plennums, al-

temately spaced around said discs,

the disc openings defining the outlet plennums are generally elliptical,and the disc openings defining the inlet plennums are generallytriangular and pointed toward the axis of the discs, said triangularinlet openings having concave sides generally concentric of the adjacentconvex sides of the outlet plennum openings, and

the generally radially extending corrugations of the first and secondplates are curved in generally concentric relation with the sides of theplennum openings between which they extend, and

the cross corrugations of the first plates are generally concentric ofthe axis of the discs.

7. A heat exchanger comprising inlet and outlet connections respectivelyprovided for first and second fluids,

a plurality of annular discs, defining alternate heat exchange flowpaths for the first and second fluids as the flow between the respectiveinlet and outlet connections therefor,

the inlet and outlet connections for the first fluid including inlet andoutlet plennums extending longitudinally of said discs and defined byopenings therein, one of said plennums being generally elliptical incross section with the major axis thereof generally radial of saiddiscs, the other of said plennums being generally triangular and pointedtoward the axis of the discs, the sides of the triangular openings beinggenerally concave and concentric of the adjacent convexly curved sidesof the elliptical openings,

the heat exchange flow paths for the first fluid pass between said discsfrom the inlet plennums to the outlet plennums and the heat exchangeflow paths for the second fluid pass between alternate plates from theinterior to the exterior of the discs, and

alternate plates comprise series of corrugations, be-

tween each adjacent plennum, which corrugations extend generallyradially of the discs and are curved generally concentric of the sidesof the plennums between which they extend.

{ 3 33 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent NO-3,83l,674 Dated Agggggi; 22 1,224

Inventor(s) Wolfgang J. Stein and Salvatore Straniti It is certifiedthat error appears in the above-identified patent and that saidLetters'Patent are hereby corrected as shown below:

Column 3, line 11,. "thhe" should read the Column 4, line 28 "feshion."(first occurrence) should read bellows Signed and sealed this 19th dayof November 974.

SEAL) Attest:

McCOY M. GIBSON JR. c. MARSHALL DAQNN Attesting Officer Commissioner ofPatents

1. A heat exchanger comprising inlet and outlet connections respectivelyprovided for first and second fluids, a relatively thin, first platehaving first and second series of corrugations, one series beingdisposed, generally, at right angles to the other, a pair of secondplates disposed, respectively, on opposite sides of said first plate,said second plates, in combination with said first plate, defining, onopposite sides thereof, portions of flow paths between the respectiveinlet and outlet connections for the first and second fluids, saidsecond plates each having a series of corrugations generally alignedwith the first series of corrugations of the first plate and generallyat right angles to the second series of corrugations, or crosscorrugations, of the first plate, whereby opposite sides of the firstplate define portions of the heat exchange flow paths for both the firstand second fluids, which flow paths provide a maximum of turbulence byarea variations both longitudinally and transversely of the flowdirections, with a minimum impedence to fluid flow.
 2. A heat exchangeras in claim 1 wherein the cross corrugations of the first plate engagethe corrugations of the second plates on opposite sides thereof, and thecorrugations of said first series are of a lesser height than that ofthe cross corrugations, the spacing of the corrugations of said firstseries matches the spacing of the corrugations of the second plates, thecorrugations of said first series are ''''out of phase'''' with thecorrugations of the second plates.
 3. A heat exchanger as in claim 2particularly adapted for use in combination with a gas turbine engine toincrease the energy level of pressurized air (first fluid) bytransferring heat thereto from the hot gas (second fluid) discharge ofthe engine as the pressurized air passes from the engine''s compressorto its combustor, said heat exchanger further including successive firstand second plates, the latter also being relatively thin, alternatelydisposed and defining alternate heat exchange flow paths for thepressurized air and the hot gas, said first and second plates beIng inthe form of annular discs forming a central entrance connection for thehot gas and an outer outlet connection therefor, said discs alsoincluding longitudinal plennums, formed by openings therethrough,providing the inlet and outlet connections for the pressurized air toand from the heat transfer flow paths defined by the first and secondplates, and further wherein the corrugations of the second plates extendgenerally radially of the discs and open to the inner and outer portionsthereof to connect the heat exchange flow paths for the hot gas to theinlet and outlet connections therefor.
 4. A heat exchanger as in claim 2wherein adjacent first and second plates have inner and outer peripheralflanges respectively joined to form the heat exchange flow path for thepressurized air therebetween as the pressurized air flows from the inletto the outlet plennums, and pairs of plates so joined are in turn joinedto adjacent pairs by seaming peripherally of the plennum openingstherein, whereby the discs are connected in bellows fashion with theseveral heat exchange flow paths for the pressurized air and the hotgas, respectively, separated from each other.
 5. A heat exchanger as inclaim 4 wherein each plate has radial, flow path defining corrugationsof the same height as the cross corrugations, said flow path definingcorrugations being being disposed on opposite sides of the inlet plennumopenings and extending from from the inner peripheral flanges andterminating in radially spaced relation from the outer peripheralflanges, said flow path defining corrgations also being disposed onopposite sides of the outlet plennum openings and extending from theouter peripheral flanges and terminating in radially spaced relationfrom the inner peripheral flanges, said flow path defining corrugationsengaging corrugations of the second plate with which it is paired, todefine the lateral bounds of the pressurized air flow paths betweenadjacent plennums, said cross corrugations being spaced from the innerand outer flanges, whereby the pressurized air is directed from outer,inlet chambers, radially inwardly through primary zones of heat transferand then through inner, exit chambers, and further wherein the firstseries of corrugations of the first plates extend radially to the innerand outer flanges thereof and cross corrugations of the sameintermediate height are formed inwardly and outwardly of the full heightcorrugations to provide a waffle effect in the portions of the firstplates which define the inlet and exit chambers.
 6. A heat exchanger asin claim 5 wherein there are a plurality of inlet and outlet plennums,alternately spaced around said discs, the disc openings defining theoutlet plennums are generally elliptical, and the disc openings definingthe inlet plennums are generally triangular and pointed toward the axisof the discs, said triangular inlet openings having concave sidesgenerally concentric of the adjacent convex sides of the outlet plennumopenings, and the generally radially extending corrugations of the firstand second plates are curved in generally concentric relation with thesides of the plennum openings between which they extend, and the crosscorrugations of the first plates are generally concentric of the axis ofthe discs.
 7. A heat exchanger comprising inlet and outlet connectionsrespectively provided for first and second fluids, a plurality ofannular discs, defining alternate heat exchange flow paths for the firstand second fluids as the flow between the respective inlet and outletconnections therefor, the inlet and outlet connections for the firstfluid including inlet and outlet plennums extending longitudinally ofsaid discs and defined by openings therein, one of said plennums beinggenerally elliptical in cross section with the major axis thereofgenerally radial of said discs, the other of said plennums beinggenerally triangular and pointed toward The axis of the discs, the sidesof the triangular openings being generally concave and concentric of theadjacent convexly curved sides of the elliptical openings, the heatexchange flow paths for the first fluid pass between said discs from theinlet plennums to the outlet plennums and the heat exchange flow pathsfor the second fluid pass between alternate plates from the interior tothe exterior of the discs, and alternate plates comprise series ofcorrugations, between each adjacent plennum, which corrugations extendgenerally radially of the discs and are curved generally concentric ofthe sides of the plennums between which they extend.